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Antenna question
- Thread starter Rondoc
- Start date
coperelectronics.com carries the sirio version. and dnjradio.com also carries the sirio
sirio m400, cte
tx hotrod, the cte version of a starduster at copper is a skylab t233. copper has reviews on that one. one review says you have to drill out the so-239 to fit a pl-259. not enough room to correctly fit the connector. Then I went to amazon and read the reviews of the sirio m400 and really not flattering. I see
now why people are hunting up the older versions of antennas!
tx hotrod, the cte version of a starduster at copper is a skylab t233. copper has reviews on that one. one review says you have to drill out the so-239 to fit a pl-259. not enough room to correctly fit the connector. Then I went to amazon and read the reviews of the sirio m400 and really not flattering. I see
now why people are hunting up the older versions of antennas!
Any gain figure with out the 'qualifier' on the end of it, the 'd' for dipole or 'i' for isotropic, is meaningless. That 'd' or 'i' tells you what something has gain over, what it is being compared to. Without knowing what an antenna is being compared with the gain rating doesn't mean anything. It could be compared to a beer can in your yard, for instance, and whatever it is it'd probably have lots of gain.
The industry standard for gain comparison is either half wave dipole. That holds true for a 'real live' comparison or an isotropic one as far as gain is concerned. A typical 1/4 wave vertical has a negative gain. A half wave antenna has zero, or unity gain (that's what everything is compared to). And a 5/8 wave antenna has some gain, not much, less than 2 dBd, but at least some. There are a lot of things that can make those figures change a bit, but that's the basic gain of those three types of antennas.
There are a number of 'ways' to misconstrue those gain figures and antenna manufacturers take advantage of every one of them to inflate their product's 'gain'. It's advertising, has little relation to reality, you know?
The biggest difference between those three antennas are their radiation patterns, their shape. Not the 'size' of those patterns but their shape, 'where' they put a signal. Out put power determines the 'size' of those patterns. That's a very 'simple' way of explaining it and there are factors that can change radiation patterns sizes and shapes. It's not fixed, it's variable to some degree.
That 'negative' gain figure for a 1/4 wave antenna certainly does not mean they are not good antennas, they are. It's just a -relative- thingy. Getting too tied up with gain figures isn't the best thing in the world to do without understanding exactly what they mean.
- 'Doc
The industry standard for gain comparison is either half wave dipole. That holds true for a 'real live' comparison or an isotropic one as far as gain is concerned. A typical 1/4 wave vertical has a negative gain. A half wave antenna has zero, or unity gain (that's what everything is compared to). And a 5/8 wave antenna has some gain, not much, less than 2 dBd, but at least some. There are a lot of things that can make those figures change a bit, but that's the basic gain of those three types of antennas.
There are a number of 'ways' to misconstrue those gain figures and antenna manufacturers take advantage of every one of them to inflate their product's 'gain'. It's advertising, has little relation to reality, you know?
The biggest difference between those three antennas are their radiation patterns, their shape. Not the 'size' of those patterns but their shape, 'where' they put a signal. Out put power determines the 'size' of those patterns. That's a very 'simple' way of explaining it and there are factors that can change radiation patterns sizes and shapes. It's not fixed, it's variable to some degree.
That 'negative' gain figure for a 1/4 wave antenna certainly does not mean they are not good antennas, they are. It's just a -relative- thingy. Getting too tied up with gain figures isn't the best thing in the world to do without understanding exactly what they mean.
- 'Doc